The present invention relates to a conveyor belt cleaner and tensioning arrangement, and in particular to a conveyor belt cleaner and tensioning arrangement wherein the scraper blades of the conveyor belt cleaner have a blade face which provides initial and subsequent full-face contact with the conveyor belt and wherein the scraper blades maintain a substantially constant cleaning angle with the surface of the conveyor belt and engage the conveyor belt with a substantially constant scraping pressure during the wear life of the scraper blades.
Conveyor mechanisms utilize an endless conveyor belt to transport bulk material, such as sand, gravel, coal and other bulk materials, from one location to another. Such a conveyor utilizes a rotating drum at each end of the moving belt. As the bulk material is discharged from the moving conveyor belt, a portion of the bulk material often remains adhered to the outer surface of the conveyor belt. Conveyor belt cleaners, including one or more scraper blades, are used to scrape the adherent material from the belt on its return run and thereby clean the belt. The scraper blades of a conveyor belt cleaner are removably attached to a rotatable cross shaft that extends transversely across the width of the conveyor belt. A tensioning device is attached to the cross shaft and applies a rotational biasing force to the cross shaft which in turn rotates the tips of the scraper blades into scraping engagement with the conveyor belt.
Scraper blades made for contacting the belt on the curvature of the discharge pulley were previously made such that just the scraping edge of the blade face surface initially engaged the conveyor belt, rather than the entire or full blade face surface, when installed. This edge contact type of blade design cleans with high efficiency when new, but after the blade wears for a short period of time cleaning effectiveness is lost. Scraper blades that provide full-face contact between the face surface of the blade and the conveyor belt, such as those of the present invention, can be designed to maintain constant cleaning efficiency over their wear life. Full-face contact blades extend the life of the scraper blade, particularly on high speed conveyors because a full-face contact blade has more mass to absorb the heat of friction generated with the rotating belt. Full-face blades reduce a problem known as feathering which occurs with primary cleaner blades when just the scraping edge engages the belt.
The present invention also enables a scraper blade to operate with a substantially constant cleaning angle and scraping pressure. The tips of primary scraper blades engage the curved surface of the conveyor belt at the head pulley of the conveyor and form a cleaning angle between the conveyor belt surface and the front surface of the scraper blade at the scraping edge of the front surface. The tip of each scraper blade also includes a scraping surface that engages the surface of the conveyor belt. The scraping surface engages the surface of the conveyor belt with a scraping pressure that is approximately equal to the scraping force with which the scraper blade engages the conveyor belt divided by the area of the scraping surface of the scraper blade.
During operation, the scraping edge and the scraping surface of each scraper blade wears due to its scraping engagement with the moving conveyor belt coated with abrasive bulk solids. The tensioner rotates the cross shaft and the scraper blades to maintain the scraper blades in biased scraping engagement with the conveyor belt. As the scraper blades wear and are rotated into continuing engagement with the conveyor belt, the orientation of the scraper blades with respect to the conveyor belt changes, which typically causes a change in the cleaning angle between the surface of the conveyor belt and the front surface of the scraper blade at the scraping edge, and a change in the scraping pressure with which the scraper blade engages the conveyor belt. In order to maintain optimum cleaning of the surface of the conveyor belt, and to achieve maximum scraper blade life and performance, the cleaning angle between the scraper blades and the conveyor belt surface, and the scraping pressure with which the scraper blades engage the conveyor belt, should remain substantially constant during the wear life of the scraper blades as the scraper blades wear and are rotated into continuing engagement with the conveyor belt. One approach to partially solving this problem is shown in U.S. Pat. No. 4,917,231 owned by the applicant herein.